1. Field of the Invention
The present invention relates to device for retaining a tube on a bending machine and more particularly to a device for selectively retaining or moving the tube relative to a bending head of the machine.
2. Brief Description of the Related Art
There are known tube bending machines which comprise an elongated frame along which moves a first movable carriage secured to a gripper for holding the tube to be bent, a second carriage movable independently of the first and carrying a mandrel or mouse disposed within the tube and a bending head.
The first movable carriage comprises a gripper which grips the tube to be bent to move it in longitudinal translation and/or rotation, as a function of pre-selected positions relative to tools carried by a bending head.
For a bending operation, the first movable carriage advances and turns the tube about its longitudinal axis to position it relative to the bending tools carried by the bending head. The second movable carriage positions, within the tube and in the bending zone, the mandrel or a mouse to ensure the bending of the tube and to avoid its flattening during deformation.
Thus, gripping and bending tools coact so as to grip a forward portion of the tube in which the mandrel or mouse is not located. The gripping and bending tools are driven simultaneously in rotation about a substantially vertical axis to permit the bending of the tube. This gives rise to the curving of the tube about the bending tool.
After the tube is bent, the tools are retracted, the first movable carriage is advanced to position the tube for a new bending operation and the second movable carriage is moved to withdraw the mandrel or its mouse from its position within the tube.
The assembly of the bending head comprises an assembly with a fixed arm in which is mounted the mechanism for driving in rotation the bending tool. On the stationary arm is also mounted the mechanism for actuating the pressing tool. An assembly with a swinging bending arm is mounted on the assembly with a fixed arm so as to be secured in rotation to the bending tools about the axis of these latter, and this assembly carries gripping tools and their actuating mechanism.
The machine is preferably controlled entirely automatically so as to carry out a series of bending operations on a given tube.